Plastic fastener

ABSTRACT

A plastic fastener is disclosed. The fastener may be employed in a vehicle generator. The fastener has a plastic body extending through an aperture of a first component and through an aperture of a second component. The body has a first distal head that retainingly abuts the opening of the aperture of the first component. The plastic body also has a second distal head that retainingly abuts the opening of the aperture of the second component. The configuration of the body secures the first component to the second component. The invention further provides a method of fastening components of a vehicular generator. A plastic body with first and second studs is over molded about a first generator component. At least one stud may be extended through an aperture of a second generator component. The studs are then formed into distal heads to secure the first component to the second component.

TECHNICAL FIELD

[0001] The present invention relates to a plastic fastener and a methodof fastening components.

BACKGROUND OF THE INVENTION

[0002] A conventional vehicular generator, sometimes referred to as analternator, includes a variety of electrical components, such as apositive heat sink, a rectifier bridge, a brush box, and a voltageregulator. These components are commonly secured to each other and/or tothe generator frame. Mounting the components in this fashion enhancesheat transfer within the generator, secures the electrical components soas to reduce damaging vibrations, and may provide electrical grounds andpositive electrical connections between various components.

[0003] The electrical components are commonly mounted with threadedfasteners, such as screws. However in order to maintain electricalisolation between the fastener, components, and frame, plastic or otherinsulators are typically required. Such an approach is shown in U.S.Pat. No. 6,034,012 to Chen et al., which depicts a mounting bolt (255)having an insulator (256) for insulating the slip ring end housing (74)from the rectifier (252). A similar approach is also shown in U.S. Pat.No. 5,712,517 to Schmidt et al., which illustrates rivets (75) withrivet insulators (76) that are used to secure an interconnection plate(70) to an upper surface (9) of a control plate/heat sink (10).

[0004] Nevertheless, the typical method of securing generator componentswith insulated threaded fasteners presents several challenges. To avoidloosening of the fastener, the fastener must be maintained at a hightension. This tension results in a continuously high compressive load onthe plastic insulator at high temperatures. Under such a load, theplastic insulator may creep, and loosen the fastener. Loose fastenersmay lead to a lower compressive load on the components in the stack-up,which may deteriorate the necessary electrical contact between thecomponents.

[0005] There is consequently a need in the art for a vehicular generatorfastener, and/or a method of fastening components of a vehiculargenerator, that overcomes one or more of the above limitations.

SUMMARY OF THE INVENTION

[0006] One object of the present invention is to provide a solution toone or more problems set forth above. One advantage of the presentinvention is that a plastic fastener, as disclosed herein, replaces moreexpensive steel screws and related accessories, such as compressionlimiters, and/or spring elements like crest-cup washers. Since thepresent invention serves as both a fastener and an insulator, it moreefficiently utilizes available package space where the accommodation ofboth metal fasteners and necessary insulation may be required. Inaddition, as the plastic fastener is an electrical insulator, theinventive fastener reduces local grounding of the components, such assalt bridging. Moreover, because the plastic fastener is more flexiblethan a metal screw, greater tolerances may be designed in the stack upof mating components; that is, the mounting aperture of a firstcomponent need not align exactly with the mounting aperture of a secondcomponent.

[0007] It is a primary object of the present invention to overcome theforegoing problems and/or to satisfy at least one of the aforementionedneeds. The invention provides a plastic fastener for a vehiculargenerator having a body that extends through an aperture of a firstcomponent of the generator and that extends through an aperture of asecond component of the generator. The plastic body has a first distalhead that retainingly abuts an outer opening of the aperture of thefirst component. The plastic body also has a second distal head thatretainingly abuts an outer opening of the aperture of the secondcomponent. The configuration of the plastic body secures the firstcomponent to the second component.

[0008] The invention further provides a method of fastening componentsof a vehicular generator. A first component of the generator isprovided. The first component has an aperture. A plastic body isextended through the aperture of the first component. The plastic bodyhas a first stud end and a second stud end. The second stud end isextended through an aperture of a second component of the generator. Thefirst stud is then formed into a first distal head that retaininglyabuts an outer opening of the aperture of the first component. Thesecond stud is formed into a second distal head that retainingly abutsan outer opening of the aperture of the second component. This methodsecures the first component to the second component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will now be described, by way of example,with reference to the accompanying drawings, in which:

[0010]FIG. 1 is a cross sectional view of a partially manufacturedplastic fastener according to the present invention in one environmentof a vehicular generator.

[0011]FIG. 2 is a cross sectional view of a fully manufactured plasticfastener according to the present invention in the environment shown inFIG. 1.

[0012]FIG. 3 is a cross sectional view of a fully manufactured plasticfastener according to the present invention in another environment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Referring now to the Figures wherein like reference numerals areused to identify identical components in the various views, FIG. 1depicts a partially manufactured plastic fastener 10 in one embodimentof a vehicular generator. Fastener 10 may be constructed in a mannermore fully described below. Fastener 10 may be used to secure one ormore components of a vehicular generator to another component. In theembodiment shown in FIG. 1, fastener 10 is utilized in a rectifierassembly 12, and specifically is positioned to secure a positive heatsink 14 and terminal assembly 16 to a slip ring end (SRE) frame 18.

[0014] In order to more fully appreciate the inventive fastener 10, thesurrounding environment of FIG. 1 will first be described in moredetail. Rectifier assembly 12 is provided to rectify the output voltageof an alternating current generator. It may be used as part of anair-cooled or water-cooled generator. Positive heat sink 14 may begenerally arc shaped and may be made out of a thermally and electricallyconductive material, such as aluminum. Positive heat sink 14 may includeone or more diode mounts 20, and one or more apertures 22 for supportingfastener 10 in the manner described below.

[0015] Each diode mount 20 is adapted to retain a respective diode 24 ina thermally and electrically conductive manner; Heat from diode 24 istransferred to heat sink 14 to provide the desired heat sink effect.Diode 24 may be of the press-fit variety. In the depicted environment,press-fit diode 24 is commonly referred to as a positive-side diode, andheat sink 14 is commonly referred to as a positive heat sink since apositive direct voltage is developed on heat sink 14.

[0016] SRE frame 18 provides an outer portion of a housing structure forthe generator. It cooperates with a drive end frame (not shown) todefine an interior space (not shown) to house a rotor assembly (notshown). SRE frame may be made out of cast aluminum, or other suitablethermally and electrically conductive material. SRE frame 18 may includeone or more diode mounts 26, and one or more through bores, orapertures, 28 for supporting fastener 10 in the manner described below.

[0017] In the environment shown in FIG. 1, SRE frame 18 additionallyserves as a negative heat sink. Each diode mount 26 is adapted to retaina respective diode 30 in a thermally and electrically conductive manner.Heat from diode 30 is transferred to SRE frame 18 to provide the desiredheat sink effect. Like diode 24, diode 30 may be of the press-fitvariety. In the depicted environment, press-fit diode 30 is commonlyreferred to as a negative-side diode, and SRE frame 18 may serve as anegative heat sink since a negative direct voltage is developed on SREframe 18.

[0018] Terminal assembly 16 may be provided for electrically connectingphase leads (not shown) from a stator to diodes 24, 30, in a manner notdepicted herein. Terminal assembly 16 may be made from an electricallyconductive material, such as copper, and may further include anovercoating of plastic, or other electrically insulating material, whichmay provide additional rigidity. Terminal assembly 16 may include anaperture 32 for receiving fastener 10.

[0019] Rectifier assembly 12 may also include rear cover 34. Cover 34may be a plastic cover with air flow passages (not shown). Cover 34 maybe provided to protect the generator from inadvertent grounding, and mayassist in preventing contamination of the generator.

[0020] With the recitation of the foregoing environment, a preferredembodiment of the inventive fastener, and method of fastening, will nowbe detailed. Fastener 10 may be made from a variety of plastics that aredurable enough to withstand loads of 0-50 Newtons and temperatures of−40 to 150 degrees Celsius. Notwithstanding the foregoing force andtemperature ranges for the above described environment, those skilled inthe art will recognize that the inventive fastener may accommodate otherranges in other environments in which the fastener may be employed.

[0021] Fastener 10 may generally include a body 36, a stud 38, and astud 40. Body 36 extends through aperture 22 of heat sink 14 and throughaperture 28 of SRE frame 18. Body 36 may additionally extend throughaperture 32 of terminal assembly 16. Stud 38 extends beyond aperture 22and, if fastener 10 is utilized to secure terminal assembly 16, thenstud 38 extends beyond aperture 32. Stud 40 extends beyond aperture 28.

[0022] Fastener 10 may be formed by over molding body 36, stud 38, andstud 40 about heat sink 14. In particular, aperture 22 may be pierced,or sledged, in heat sink 14, such that upper lip 42 and lower lip 44 ofaperture 22 are formed. Body 36, with stud 38 and stud 40, may then beover molded within aperture 22. Upper lip 42 and lower lip 44 provideadditional surface area to anchor fastener 10 to heat sink 14.Specifically, upper lip 42 and lower lip 44 define outer lip surfaces 46and inner lip surfaces 48 to anchor fastener 10 at either high or lowtemperature extremes of the surrounding environment. During lowtemperature extremes, fastener 10 contracts down on surface 46 tightly.Similarly, in high temperature extremes fastener 10 expands towardsurface 48 tightly. Accordingly, at either temperature extreme fastener10 may hold the components of the generator securely.

[0023] As shown in FIG. 1, body 36 may extend beyond aperture 22 and beover molded and disposed about heat sink 14. Upon being formed aboutheat sink 14, stud 40 may be positioned through aperture 28, and stud 38may be optionally extended through aperture 32. It will be appreciatedby those skilled in the art that fastener 10 may be formed about heatsink 14 through other conventional methods. Moreover additionalfasteners, such as the partially shown fastener 10A in FIG. 1, may beemployed within an environment of a vehicular generator.

[0024]FIG. 2 depicts fastener 10 in a completely manufactured form 10′.In fastener 10′, stud 38 and stud 40 have been formed into distal head50 and distal head 52, respectively. Distal head 50 abuts aperture 32 toretain heat sink 14. As shown in FIG. 2, terminal assembly 16 may beinterposed between heat sink 14 and distal head 50, such that distalhead 50 abuts aperture 32 to secure terminal assembly 16 relative toheat sink 14. Similarly, distal head 52 abuts aperture 28 to secure heatsink 14 to SRE frame 18.

[0025] Distal head 50 and distal head 52 may be formed by ultrasonicwelding stud 38 and stud 40. Those skilled in the art will appreciatethat other manufacturing methods, such as heat staking, may be similarlyeffective in forming distal heads 50 and 52. Distal head 50 is formedsuch that it has a diameter larger than the diameter of the opening ofaperture 32 to which it abuts. Similarly, distal head 52 is formed suchthat it has a diameter larger than the diameter of the opening ofaperture 28 to which it abuts.

[0026] While FIGS. 1 and 2 depict fastener 10 and 10′ in one environmentof a vehicular generator, it will be appreciated by those skilled in theart that the inventive fastener 10′ may be employed in otherenvironments where similar benefits can be realized. FIG. 3 representsthe utilization of fastener 10′ to secure components in other suchenvironments. Fastener 10′ is shown in FIG. 3 with its body 36, distalhead 50, and distal head 52. In this environment, for example, fastener10′ may secure one component 54 to a second component 56. Suchcomponents may include, for example, a brush box assembly and voltageregulator, respectively.

[0027] Like heat sink 14, component 54 includes an aperture 58 that maybe pierced, or sledged, to form an upper lip 60 and a lower lip 62. Lips60 and 62 define outer lip surface 64 and inner lip surface 66 forsecuring body 36 when it contracts and expands, respectively, at varyingoperating temperatures of the environment. Like SRE frame 18, component56 includes an aperture 68. Distal head 50 and distal head 52retainingly abut the outer openings of aperture 58 and aperture 68,respectively, to secure component 54 to component 56. While apertures 58and 68 are coaxial in the illustrated embodiment, it will be appreciatedby those skilled in the art that due to the flexibility of fastener 10′,both inherently and since it may be over molded to in a variety ofshapes, apertures 58 and 68 may be offset from each other.

[0028] The present invention may be employed in any application wherethe retention stress on the joint to be fastened is within thecapabilities of the plastic material chosen. Further, the inventivefastener may be beneficially employed in environments which are exposedto temperature fluctuations.

[0029] While the present invention has been described with reference tocertain preferred embodiments and implementations, it is understood thatvarious modifications and variations will no doubt occur to thoseskilled in the art to which this invention pertains. These and all othersuch variations which basically rely of the teachings through which thisdisclosure has advanced the art are properly considered within the scopeof this invention.

1. A plastic fastener for a vehicular generator, comprising: a bodyextending through an aperture of a first component of said vehiculargenerator and said body extending through an aperture of a secondcomponent of said vehicular generator, said body having a first distalhead retainingly abutting an outer opening of said aperture of saidfirst component, and said body having a second distal head retaininglyabutting an outer opening of said aperture of said second component,whereby said first component is secured to said second component.
 2. Theplastic fastener of claim 1, wherein said body is retaininglycontractable about an outer lip surface of said aperture of said firstcomponent, and wherein said body is retainingly expandable about aninner lip surface of said aperture of said first component.
 3. Theplastic fastener of claim 1, wherein said first distal head has adiameter larger than the diameter of said aperture of said firstcomponent, and said second distal head has a diameter larger than thediameter of said aperture of said second component.
 4. The plasticfastener of claim 1, wherein said first component comprises a heat sinkand said second component comprises a slip ring end frame.
 5. Theplastic fastener of claim 1, wherein said body further extends throughan aperture of a third component of said vehicular generator, said thirdcomponent interposed between said first component and said first distalhead.
 6. The plastic fastener of claim 5, wherein said first componentcomprises a heat sink, said second component comprises a slip end frame,and said third component comprises a terminal assembly.
 7. The plasticfastener of claim 1, wherein said first component comprises a brush boxand said second component comprises a voltage regulator.
 8. The plasticfastener of claim 1, wherein said aperture of said first component andsaid aperture of said second component are coaxial.
 9. The plasticfastener of claim 1, wherein said aperture of said first component andsaid aperture of said second component are axially offset.
 10. A methodof fastening components of a vehicular generator, comprising: providinga first component of said vehicular generator, said first componenthaving an aperture; extending a plastic body through said aperture offirst component, said body having a first stud end and a second studend; extending said second stud through an aperture of a secondcomponent of said vehicular generator; forming said first stud into afirst distal head that retainingly abuts an outer opening of saidaperture of said first component; and forming said second stud into asecond distal head that retainingly abuts an outer opening of saidaperture of said second component, whereby said first component issecured to said second component.
 11. The method of claim 10, whereinsaid steps of forming said first and second studs comprise ultrasonicwelding said first and second studs.
 12. The method of claim 10, whereinsaid steps of forming said first and second studs comprise heat stakingsaid first and second studs.
 13. The method of claim 10, wherein saidstep of extending said plastic body through said aperture of said firstcomponent comprises over-molding said plastic body in said aperture ofsaid first component.
 14. The method of claim 13, wherein saidover-molding comprises over-molding said plastic body in an aperture ofa heat sink of said vehicular generator.
 15. The method of claim 14,wherein said step of extending said second stud comprises extending saidsecond stud through a slip ring end frame of said vehicular generator.16. The method of claim 14, further comprising extending said first studthrough a terminal assembly of said vehicular generator.
 17. The methodof claim 10, wherein said step of extending said first stud comprisesextending said first stud through an aperture in a voltage regulatorassembly of said vehicular generator and wherein said step of extendingsaid second stud comprises extending said second stud through slip ringend frame of said vehicular generator.
 18. A plastic fastener,comprising: a body extending through an aperture of a first componentand said body extending through an aperture of a second component, saidbody having a first distal head retainingly abutting an outer opening ofsaid aperture of said first component, and said body having a seconddistal head retainingly abutting an outer opening of said aperture ofsaid second component, whereby said first component is secured to saidsecond component.